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Pruritus ani
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Exam Tips
- In OSCEs, state early that pruritus ani is a symptom, then separate primary from secondary causes and actively look for red flags.
- A careful external perianal exam (with chaperone) plus targeted history often provides diagnosis without extensive tests.
- Night-time itch in a child strongly suggests threadworm; household contact symptoms suggest scabies.
- Topical steroid use should be short and low potency (e. g, hydrocortisone up to 7 days); prolonged use can worsen skin damage.
- Always mention urgent 2-week colorectal referral when cancer is suspected (bleeding, change in bowel habit, weight loss, mass, persistent pain).
Definition
Pruritus ani is persistent or recurrent itching/burning of the perianal skin and is a symptom complex rather than a single diagnosis. It is classified as primary (idiopathic, often linked to local faecal irritation) or secondary, where an underlying dermatological, infective, anorectal, systemic, drug-related, or psychosocial cause is identified.
Pathophysiology
The dominant mechanism is an itch-scratch cycle at the anoderm/perianal skin interface. In primary disease, minor faecal seepage, moisture, friction, and over- or under-cleansing disrupt the skin barrier, allowing irritants/allergens (including bacterial enzymes) to trigger inflammation and neural itch signalling; repeated scratching then causes excoriation, lichenification, and further barrier failure. Secondary pruritus ani follows the same final pathway but is driven by a specific trigger (for example eczema, candidiasis, threadworm, haemorrhoids, fissure, contact allergy, or systemic illness). For visual revision, see a standard dermatology text figure of the itch-scratch cycle and lichen simplex chronicus ("See Figure from page X").
Risk Factors
- Male sex (around 4:1 compared with women)
- Age 40-60 years
- Faecal contamination/seepage, loose stool, chronic diarrhoea, constipation with soiling
- Excess sweating, occlusive clothing, poor ventilation of perianal area
- Aggressive hygiene practices (frequent soaps/perfumes/wet wipes) or inadequate cleansing
- Dermatoses: atopic eczema, psoriasis, seborrhoeic dermatitis, lichen sclerosus/planus
- Infections/infestations: Candida, bacterial perianal infection, HSV, HPV, threadworm, scabies, STIs
- Anorectal pathology: haemorrhoids, fissure, fistula, anorectal neoplasia
- Systemic disease: diabetes, liver/kidney disease, thyroid disease, haematological disease/anaemia
- Dietary triggers (for some patients): coffee, alcohol (beer/wine), spicy/citrus/tomato/nuts/dairy
- Drug exposure: antibiotics (e. g. tetracycline, metronidazole), colchicine, peppermint oil, topical anaesthetics/corticosteroids causing contact dermatitis
Clinical Features
Symptoms
- Perianal itching (often worse after stooling, sweating, or at night)
- Burning/soreness, irritation, or stinging around anus
- Sleep disturbance, irritability, reduced concentration/daytime fatigue
- Nocturnal itch in children suggests threadworm
- Associated bowel symptoms: leakage/soiling, constipation, diarrhoea
- Red-flag associated symptoms: rectal bleeding, change in bowel habit, weight loss, persistent pain, mass sensation
Signs
- Mild erythema in early disease
- Excoriations, fissuring, or moist dermatitis in active scratching
- Lichenification/shiny thickened perianal skin in chronic disease
- Secondary infection signs (crusting, pustulation, tenderness)
- Visible anorectal causes on inspection: external haemorrhoids, fissure, fistula opening, dermatitis pattern
- Possible perianal mass/induration on examination requiring urgent cancer pathway consideration
Investigations
Focused history (pattern/triggers, bowel habit, hygiene products, medication, sexual history, systemic symptoms):Identifies likely secondary cause or trigger; nocturnal itch points to threadworm, household spread raises scabies likelihood
Perianal inspection with chaperone and lateral positioning:Defines severity (erythema vs excoriation/fissures/lichenification) and may reveal haemorrhoids, fissure, dermatitis, infection
Digital rectal examination in adults when tolerable:Screens for underlying anorectal pathology including mass lesions
Perianal skin swab for microscopy/culture/sensitivity:Detects bacterial or candidal superinfection and guides antimicrobial therapy
Patch testing/dermatology assessment:Supports allergic contact dermatitis if history suggests topical/contact trigger
Lower GI investigation (e. g, colorectal referral with endoscopic assessment when indicated):Excludes structural colorectal/anal disease including malignancy in red-flag presentations
Targeted tests for suspected causes (e. g, tape test for Enterobius in children, STI testing, bloods for diabetes/thyroid/anaemia/liver/renal disease):Confirms secondary aetiology and directs definitive treatment
Management
Lifestyle Modifications
- Treat any identified underlying cause first (dermatological, infective, anorectal, systemic, or drug-related)
- Gentle perianal care: wash with plain water after bowel motions and at bedtime if practical; avoid soaps, perfumes, scented wipes, and over-scrubbing
- Dry by patting (not rubbing); consider cool air drying; keep area dry and reduce moisture/friction
- Use loose, breathable cotton underwear; avoid tight/occlusive clothing and residual biological detergent irritants
- Break itch-scratch cycle: keep nails short, avoid scratching, consider cotton gloves overnight in severe nocturnal scratching
- Bowel optimisation: manage diarrhoea/constipation, improve stool consistency, reduce seepage/soiling
- Trial elimination of personal dietary triggers (e. g, caffeine/alcohol/spice/citrus) if history supports association
- Safety-net: seek review if symptoms persist beyond 3-6 weeks, worsen, or red flags occur (bleeding, weight loss, change in bowel habit, persistent pain, mass)
Pharmacological Treatment
Barrier and soothing topical preparations
- Zinc oxide-containing ointment/cream thinly to clean dry perianal skin at night, morning, and after bowel movements
- Haemorrhoidal symptom-relief products (e. g, Anusol, Germoloids) as per product directions
Useful when skin is excoriated/irritated. Prefer simple non-steroid preparations where possible, including in pregnancy/breastfeeding when risk-benefit favours treatment.
Topical corticosteroids (short course only)
- Hydrocortisone 1% cream or ointment: thin layer, up to twice daily, maximum 7 days
- Anusol-HC ointment (hydrocortisone 0.25%) short-term
- Proctosedyl ointment (hydrocortisone 0.5%) short-term
Do not use if local untreated infection is present (e. g, herpes simplex, perianal candidiasis). Overuse risks skin atrophy, sensitisation, and contact dermatitis; avoid prolonged or frequent rectal mucosal exposure.
Sedating oral antihistamine for nocturnal itch (symptom control adjunct)
- Chlorphenamine: 1 month-2 years 1 mg twice daily
- Chlorphenamine: 2-6 years 1 mg every 4-6 hours (max 6 mg/day)
- Chlorphenamine: 6-12 years 2 mg every 4-6 hours (max 12 mg/day)
- Chlorphenamine: >=12 years and adults 4 mg every 4-6 hours (max 24 mg/day; max 12 mg/day in older people)
Warn about sedation/psychomotor impairment (driving/machinery risk), additive CNS depression with alcohol, and anticholinergic effects (dry mouth, blurred vision, urinary retention). Avoid in severe liver disease; use caution in glaucoma, BPH/urinary retention, cardiovascular disease, epilepsy, asthma/bronchitis, renal/hepatic impairment, elderly, pregnancy, and breastfeeding.
Cause-directed therapy
- Treat specific confirmed causes (e. g, anthelmintic for threadworm, targeted topical/systemic antimicrobials for infection, eczema-directed dermatological therapy)
Medication choice should follow organism/diagnosis and local antimicrobial guidance; avoid empirical long-term topical combinations that perpetuate contact dermatitis.
Surgical / Interventional
- No primary surgery for idiopathic pruritus ani
- Refer urgently via suspected cancer pathway (2-week wait) if anal/colorectal malignancy suspected
- Refer to colorectal surgery/dermatology when specialist diagnosis or treatment is needed
- Definitive procedures for underlying anorectal causes when indicated (e. g, haemorrhoid interventions, fistula/fissure surgery)
Complications
- Lichen simplex chronicus and chronic lichenification
- Eczema/dermatitis with fissuring and excoriation
- Ulceration and hypertrophic/scarred perianal skin
- Secondary bacterial infection (including Staphylococcus aureus)
- Sleep disruption, anxiety/depressive symptoms, embarrassment, and reduced quality of life
Prognosis
Many patients improve with trigger avoidance, skin-barrier care, and treatment of identifiable causes, but relapse is common because pruritus ani can become chronic if the itch-scratch cycle persists. Prognosis is best when secondary causes are actively sought and managed early, with prompt referral for red-flag or refractory disease.
Sources & References
💊BNF Drug References(4)
- Benzyl benzoate with bismuth oxide, bismuth subgallate, hydrocortisone acetate, peru balsam and zinc oxide[management.pharmacological]
- Cinchocaine with hydrocortisone[management.pharmacological]
- Cinchocaine with prednisolone[management.pharmacological]
- Hydrocortisone with lidocaine[management.pharmacological]
✅NICE Guidelines(1)
- Pruritus ani[overview]
📖Textbook References(19)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1661)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1841)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 707, 708)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 708)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 708)[context]
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1841)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 645, 646)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 647)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 646)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 645, 646)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 646, 647)[context]
- [Oxford Medical Handbooks] Ian Wilkinson, Tim Raine, Kate Wiles, Anna Goodhart, Catriona Ha - Oxford Handbook of Clinical Medicine (2017, Oxford University Press) - libgen.li.pdf(pp. 644, 645)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1275)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1273, 1274)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1273, 1274)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1274, 1275)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1274)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1273, 1274)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1274)[context]